This book constitutes the refereed proceedings of the 11th International Conference on Security, Privacy, and Applied Cryptography Engineering, SPACE 2021, held in Kolkata, India, in December 2021. The 13 full papers presented were carefully reviewed and selected from 42 submissions. This annual event is devoted to various aspects of security, privacy, applied cryptography, and cryptographic engineering. This is a very challenging field, requiring the expertise from diverse domains, ranging from mathematics to solid-state circuit design.